Calutron operation



Aug. 2, 1955 J. H. BURNEY ET AL CALUTRON OPERATION 3 Sheets-Sheet 1 Filed June 18, 1946 1955 J. H. BURNEY ET AL CALUTRON OPERATION 3 Sheets-Sheet Filed June 18, 1946 NNGWWW h m Aug. 2, 1955 J. H. BURNEY E AL CALUTRON OPERATION 5 Sheets-Sheet Filed June 18, 1946 INVENTORS. A 45 United States Patent Ofi fildfiil? Patented Aug. 2, i985 ice 2,714,667 CALUTRON OPERATION James H. Burney, Corpus Christi, Tex., and William H. Appleton, Lafayette, and Robert De Liban and George M. Farly, Berkeley, Calif., assignors to the United States of America as represented by the United States Atomic Energy Commission Application June 18, 1946, Serial No. 677,482 46 Claims. (Cl. 250-41.9)

This invention relates to calutrons and particularly to the operation of a calutron under automatic control. A calutron of the type to which my invention has particular reference and application is disclosed in detail in the earlier application of Ernest 0. Lawrence, Ser. No. 557,784, filed October 10, 1944. ratus the isotopes of a material are separated electromagnetically, the process involving ionizing vapor of the material the isotopes of which are desired and segregating the ions in a manner to produce quantities of the material enhanced with particular isotopes thereof by means of projecting the ions with an initial velocity into a strong magnetic field which causes them to travel in arcs of a circle the radii of which are dependent upon the mass-energy properties of the ions. The ions thus acted upon are brought to a focus at approximately 180 degrees from the source thereof, and the various desired isotopes focus at points separated a sufficient distance apart to permit collection of the separated isotopes at the spaced points.

The process is carried out within a highly evacuated tank and under the influence of a strong magnetic field as mentioned above, and in a calutron it is customary to use an ion source of the arc type, that is, a type of source wherein an arc is struck in the vapor of the material the isotopes of which are desired, and the positive ions formed are then projected or propagated with an initial velocity into the magnetic field region. It is usual to arrange the structure so that the vapor issues through a slit from a source thereof into an arc chamber wherein the arc is struck, the arc chamber having a second or exit slit formed through the chamber wall. An accelerating electrode having a slit formed therethrough is disposed adjacent the exit slit, external to the arc chamber, with the accelerating electrode slit arranged in alignment with the exit slit, this accelerating electrode being at a relatively high negative potential with respect to the arc source for the purpose of withdrawing positive ions from the arc region through the exit slit and projecting them with an initial velocity into the magnetic field region. There may be but a single arc source of ions in one tank; on the other hand, a plurality of ion sources and resultant ion beams may be used in a single evacuated tank. For instance, there may be two, three, or four, or more ion sources. In calutrons as described, the ion source itself is often operated at a relatively high voltage relative to ground, this type of source being commonly referred to as a hot source. As mentioned above, the accelerating electrode is at a relatively high negative potential relative to the ion source. When the ion source is operated at a high positive potential relative to ground, the accelerating electrode being at a relatively high negative potential relative to ground, the potential difference between the source and accelerating electrode is often as high as 60 or 65 kilovolts.

Because of the high voltages and because the mechanism is disposed in a high vacuum and a strong magnetic field, it has been found from experience that the appa- In this type of apparatus is quite susceptible to voltage surges and sparking as well as other related disturbances which are commonly referred to as fiurries. Sparking may occur between the ion sources and the accelerating electrode or between each of these elements and ground and such fiurries in calutrons are highly undesirable for a number of reasons. Sparking fiurries are the occasion of high electrical drains in the apparatus, that is, relatively high flows of current through the ion source, within the evacuated tank, from the ion sources to the accelerating electrode and/or ground, and from ground to the accelerating electrode. The sum of the currents from the ion sources, including that portion that constitutes the projected ion beam, will hereinafter be referred to as source or source assembly drain current, Whereas the sum of the currents flowing to the accelerating electrode will be referred to as the accelerating electrode drain current. It will be understood, of course, that external to the evacuated tank the source drain current flows to the ion source or sources and the accelerating electrodes drain current flows from the accelerating electrode. These excessive currents cause undue heating and deterioration of the equipment and furthermore militate undesirably against the efiiciency and the effectiveness of the process. Serious flurries or other sparking disturbances are usually sufficient to interrupt the operation of the system thus lowering the amount of production proportionately and furthermore they result in lowering of the enhancement of the desired isotopes being separated. The current surges involved are usually sufficient to actuate the overload responsive devices, completely cutting off the supply of power to the system, the system then being recycled, that is the power is brought back on either manually or automatically. Such action interrupts collection of isotopic material during periods in which the collector pockets are opened for the reception of desired separated isotopes therein. During such interruptions the enhanced material in the pockets becomes contaminated since the change in voltage of the ion source displaces the beam causing the open collector pockets to be exposed to the wrong components thereof. In the past it has sometimes been extremely difficult to keep the high voltages on; the system repeatedly cutting off in response to the overload responsive devices and requiring the attention of an operator to manually recycle the power supply in attempting to restore normal operation.

Our invention contemplates the provision of automatic control arrangements for calutrons arranged so as to prevent or suppress sparking flurries associated with the accelerating electrode and with the ion source itself, and in this manner thereby to improve the operation of a calutron by making the operation more uniform and steady.

With reference to the usual disturbances heretofore common to calutrons, the foregoing recites the broad object of our invention. In the past an operator has been necessary to control or operate each calutron unit, the duties of the operator being to maintain the calutron in steady uniform operation insofar as that has been possible, and the operator performing certain functions in the event of a flurry or other disturbances for the purpose of bringing the apparatus out of the flurry and reestablishing normal operation. Our invention provides an automatic control system which automatically performs a sequence of operations whereby the undesirable disturbances in the calutron operation are suppressed or adequately overcome, to the extent that operation of the overload responsive devices is materially reduced and the operation otherwise made more steady and continuous.

Another object of our invention is to provide an automatic control system in calutrons employing one or more are sources of ions wherein the amperage of at least one of the arcs is temporarily reduced in the event of excessive sparking and/or current drains to the accelerating electrode.

Another object of the invention is the provision of a system as in the previous object wherein the amperage of a plurality of ionizing arcs is reduced.

Another object of the invention is the provision of a system as in the previous two objects wherein the amperage of the single are or plurality of arcs 1S restored to normal after a time delay of a predetermined length, the time delay beginning at the time of reduction of amperage of the are or arcs. F

Another object of the invention is the provision or an automatic control system in calutrons wherein the drain current from the ion source or sources is temporarily limited to a value below normal in the event of higher than normal values of this current and/or undue sparking from the sources, that is, means are provided which limit the current which can flow.

Another object of the invention is the provision of a system as in the foregoing object wherein the limitation on current to the ion source is removed after a time delay of predetermined lengt the time period beginning at the time the limitation on the current to the ion source is made.

Another object of the invention is the provision of a control system as in the two foregoing objects wherein the apparatus for temporarily reducing the drain current to the ion source may recycle a plurality of times, for example three times, after which if the disturbance has been rectified and cleared up, the drain current to the ion source will'be reduced by a second increment.

Another object of the invention is the provision of an automatic control system in calutrons wherein in the event of undue sparking or current drains to the ion source, the drain current to the ion source will be ternporarily reduced for a predetermined period and the amperage of the arc in the ion source will simultaneously be temporarily reduced.

Another object of the invention is the provision of a control system as in the foregoing object wherein the amperage of the arc of the ion source will not be restored until after the disturbance associated with the ion source has been rectified and the limitation on ion source drain current removed.

Another object of the invention is the provision in a calutron employing a multiple arc source of means for temporarily reducing the amperage of one or more arcs in the event of excessive current drains to the accelerating electrodes and switching means for selectively choosing the are or arcs to be reduced and the amount by which each is reduced.

Another object of the invention is to provide an automatic control system in calutrons wherein in the event of excessive drains to the ion source the current to the source is reduced by means of emission limiting control tubes which control the power supply to the ion source Another object of the invention is to provide a method of quelling sparking disturbances in high voltage electrical equipment wherein an arc is struck comprising temporarily reducing the amperage of the are for a predetermined period of sufiicient length to allow the disturbance to be overcome.

Another object of the invention is to provide a method of operating a calutron of the type embodying an arc source of ions which comprises temporarily reducing the amperage of the arc in the event of sparking disturbances or the like for a period of sufficient duration to enable the disturbance to be cleared up.

Another object of the invention is to provide a method of operating a calutron of the type embodying an arc source of ions wherein an ion source is operated at a high potential comprising substantially limiting the drain current to the ion source in the event of sparking disturbances or the like for a sufiicient period of time to allow the disturbance to be cleared up.

Another object of the invention is to provide a method as in the preceding object wherein the arc amperage is simultaneously reduced for a predetermined period.

Another object of the invention is to provide a method as in the preceding object wherein the amperage of the arc is not restored until after the expiration of a preturbance has not been cleared up after the plurality of recycles.

Another object of the invention is to provide a method of operating a calutron of the arc source type wherein in the event of an overload causing the power to be cut off, upon the resumption of power the ion source drain current is temporarily limited for a predetermined timed period and the amperage of the arc is temporarily limited for apredeterrnined timed period.

Further objects of our invention and numerous of its advantages will be apparent from the following detailed description and annexed drawings,

, Fig. l ofwhich is the upper part of a wiring diagram illustrative of the automatic control system of the invention.

Fig. v2 is the middle part of the diagram, and

Fig. 3 is the lower part of the diagram.

Referring to the drawings Fig. 1 shows for the most part the automatic controls of the system; Fig. 2 shows forthe most part the manual controls or adjustments; and Fig. 3 shows in diagrammatic form certain parts of a calutron, and various power supplies therefor.

With reference to Fig. 3 of the drawing there is shown diagrammatically the manner in which a calutron employing a multiple arc ion source unit may be set up. ,As

is the usual practice in calutrons, the apparatus is inclosed within a tank (not shown) which is evacuated to a relatively low pressure; the evacuated tank is disposed in a magnetic field as indicated by the arrow which has a direction transverse to the tank. Our invention is primarily concerned with the ion source part of the calutron and the accelerating electrodes, and this part of the apparatus is designated generally at 36' on the drawing. As shown, the assembly comprises what constitutes a multiplicity of ion sources. The ion sources are assembled in '2 a manner to form two sub-assemblies which areattached to a face plate 37 by means of insulators 34 which space the ion sources from the face plate, the face plate being sealingly attachable to the evacuated tank so as to thereby support the ion source units within the tank. The ion source assembly comprises four individual units each of them having means for vaporized material to be ionized as shown. Each sub-assembly comprises a vaporizing chamber and each of the units comprises a narrower ionizing chamber as indicated at L1, L2, L3 and L4 having an exit slit therein through which the ions are emitted during the operation, the ionizing chambers being formed in pairs as shown at the outward end of their respective vaporizing chambers. The vaporizing chamhers are heated by electrical heating coils not shown, the heat therefrom serving to vaporize the material to be ionized which'is originally in the form of a solid granulated charge. Adjacent each of the exit slits is an accelerating electrode having the form of an elongated. slot parallel to'the exit slitin the ion source unit. The accele'rating electrodes'are designated by the characters G1,

G2, G3 and G4. These accelerating electrodes are maintained at a high negative potential relative to the ion sources as will be described for the purpose of withdrawing positive ions from the ionizing region. The detailed construction of the source units may be as shown in the Lawrence application referred to above and the arrangement may embody batfies between the ionizing chambers and vaporizing chambers.

Adjacent one end of each of the ion source units is a filamentary cathode which during operation emits a stream of electrons into and along the ionization chambers of the ion source units for ionizing the vapor in advance of its issuing from the slits. The cathodes are designated by the characters K1, K2, K3 and K4. The cathodes emit electrons which pass through small elongated collimating slots into the ionization chambers as shown, an are being struck in the vapor in the ionization chamber as will be described. In operation the ionized particles travel in arcs of a circle as indicated by the arrows to the grounded receivers or collectors designated Further detailed by the characters E1, E2, E3 and E4. description of the calutron itself is not necessary since it is described in detail in the earlier application referred to above.

The power supply for the ion source units which are maintained at a positive potential relative to ground of approximately 35,000 volts is supplied from a 460 volt three phase source of power (see Fig. 2). The power source 15 connects to a conventional overload responsive cut-off device or relay 38 various circuits of the system. Device 38 operates a switch causing this switch to open whenever the overload responsive device operates. Device 38 connects by three phase circuit 39 to a transformer and rectifier system designated diagrammatically at 40 which provides a relatively high voltage D. C. out ut between wires 41 and 67. This output is controlled cated at R21 through R26 (see Fig. 2) to an induction voltage regulator as indicated diagrammatically at 52 and an autotransformer 53. Associated with the variable resistances R21, R22, and R23 there is a relay RE8 which has a coil or winding 55 which operates switches 56, 57, and 58, these switches being closed when the relay is deenergized. When plete shunts across the resistances R21-R23 respectively as shown. Associated with the resistances R24, R25, and R26 is a relay RE9 having a winding or coil 59 which operates switches 60, 61, and 62, these switches being closed when the relay is deenergized. The when closed complete shunts across the resistances R24, R25, and R26 respectively as shown. The induction voltage regulator or regulators are of standard commercial type as is the autotransformer, and the output thereof is connected to two delta connected transformer pri-u maries 63 and 64 by way of center tap inductances 43, 44, and 45, the ends of each inductance connecting to corresponding taps on the two primaries. The transformers have Y connected secondaries 46 and 47 and the output of the secondaries is connected to the filamentary oath-t; odes of triode control tubes 68 and 69. The control tubes are connected in parallel as shown, the filaments connecting to the ion source assembly through wire 74) by way of the center taps of secondaries 46 and 47, and the plates connecting to wire 41 which is the positive side of the supply from system 40. Numeral 71 designates a voltage regulator connected across the output of the rectifier system 40, the regulator connecting between the wire 70 and the grids of the control tubes 68 and 69.

The regulator 71 is of known design and construction and its details form no part of my invention, its operation being to regulate the voltage between wires 67 and 70 by controlling the bias on the grids in the control tubes 68 and 69, the regulator receiving its control signal from having contacts controlling i no these switches are closed, they comlatter switches particularly to restore normal a voltage divider 76 connected between wires 67 and 70. The power supplied by the circuit 67-70 may be further controlled in accordance with our invention as will be presently described by opening the shunts controlled by relays RE8 and RE9 and thereby placing additional resistance in series with the supply to the filaments of tubes 68 and 69 to thereby emission limit these tubes. This type of operation in itself is well known in the art, that is emission limiting a tube and therefore it need not be described in further detail.

The rectified power supply for the accelerating electrodes is indicated diagrammatically at 73, the ground side being connected to ground through a wire 74 and the other side of the line connecting to the accelerating electrodes through the wire 75. This power supply is through device 38 also, as indicated by the three wire circuit 72. The power source 73 may be such as to maintain the accelerating electrodes at a negative D. C. potential of 15 kilovolts thus making the potential difiference between the accelerating electrodes and the ion sources 50 kilovolts.

As described above, our invention is primarily cor1- cerned with suppressing electrical disturbances relating to the ion source units and the accelerating electrodes and operating conditions in the event of excessive current drains to either the ion source assembly or the accelerating electrodes. As described above, during operation an arc is struck in advance of each of the eXit slits of the ion source units, and this are is sustained by a voltage connected between the cathode at the end of the slit and the ion source units, that is, the block or housing in which the charge is vaporized and ionized. On the drawing the four individual ion source units are identified by the letters J1, J2, J3 and J4, and hereafter the ion source units will be referred to using these characters, the letter I having particular reference to the ionizing are which is struck. There is a separate power supply for each of the PS, these power supplies supplying the voltage required for sustaining the arcs in advance of the exit slits of the ion sources. The arc current associated with each ion source is automatically regulated normally, so as to maintain a steady arc. The arc current regulates itself by means of its associated cathode being controlled in response to the power supplied for sustaining the arc. With reference to the arc J1, the power supply therefor is from a 460 volt 3-phase source indicated at 160. The 3-phase source is connected to a rectifier 161 which provides D. C. are current, the negative output terminal connecting to one of the cathode leads of K1 and the positive output terminal connecting to the ion source unit assembly for arcs J1 and J2 as shown. Each phase of the 3-phase source is in series with the primary of a transformer, these transformers being designated 162, 163, and 164. These transformers are current transformers and hence introduce but a small voltage drop in the arc supply primary lines, their purpose being to obtain a signal. proportional to the D. C. are current. The secondaries of these transformers are connected to the plates of rectifier tubes 165, 166 and 167 respectively. The filaments of the rectifier tubes 165, 166 and 167 are connected across the secondary of a transformer 168. The output of the rectifier system appears between wires 169 and 170 which connect respectively to the center tap of the secondary of transformer 163 and to the center taps of the secondaries of transformers 162, 163 and 164. From the foregoing it will be seen that the D. C. output of the rectifier system is proportional to the power supplied to transformer 161 from the 3-phase source 160.. The D. C. output of the rectifier system is connected across a resistance 171 and this voltage opposes a standard voltage V connected across a resistance 172 and regulated by a standard VR 105 tube 159. The juncture of the resistances 171 and 172 is connected to a device 173 by a wire 174, the device 173 constituting a conventional amplifier and control system which controls the power supplied to an insulating transformer which supplies power for the cathode K1.

The other side of the input signal circuit to device or systerm 173 is from a circuit connecting the center taps of the resistances 171 and 172, andthis circuit includes the Wires 1 and 2 across which a shunt may be placed or across which additional resistance may be placed as will be, presently described.

By reason of the transformers 161 and 175, the control system for the I are voltage does not operate at the high potential of the ion source 'units themselves. Since the voltage of the D. C. output of the rectifier system opposes the voltage across the resistance 172, the signal supplied to the device 173 will depend upon the difference in these voltages, and this,

of course, depends on the power supplied to the transformer 161 from the 3-phase source 160. Accordingly the power supplied to the cathode K1 is varied in accordance with the I are current of are lit and in normal operation the cathode power is thus automatically varied so as to maintain the arc steady. There is normally a shunt across the wires, that is, the circuits 1-2, and when it is desired to reduce the arc of J1, the shunt is opened and a resistance is connected across the circut 1-2 so as to thereby change the signal supplied to the device 173 by a fixed increment so that the amperage of the arc of I1 is thus reduced by a fixed increment, the arc, however, remaining under automatic control, without impairment thereof. Manual controls may be provided if desired for normally setting the arc current, the set value then being maintained automatically. I

The entire power supply and controlsystern or channel for are I1 is indicated by numeral 182 and rectangle.

The control systems for the arcs J2, J3, and 14 are the same as the system for the arc I1 so that detailed description of each one is not necessary. The control systems for arcs J2, J3 and I4.- are indicated diagrammatically by the numerals 176, 177 and 178, these systems or channels corresponding to that represented by numeral "132. The circuits corresponding to the circuit 1-2 for the arcs J2, J3 and M are indicated by the numerals 3-4 for 12; 5-6 for J3; and 7-3 for J4. In other words, the circuits 3-4, 5-6, and 7-3 are normally shuntedas is the circuit 1-2 and a resistance is connected across one or more of these circuits whenever it is desired to reduce the amperage of the corresponding I arc.

The resistances which are utilized for reducing the amperage of one or more of the arcs are arranged in two jgroups identified by the characters GR1 and GR2 (see :Fig. 2). The group of resistances GR1 comprises three resistances R31, R32, and R33 and these resistances are connected between a wire or lead identified 11a and individual contact points or terminals 78a, 73b and 780 and there is an additional contact point or terminal 78 connected to wire 11a. Numeral 79 designates a manually operable switch blade which is movable between all of :the terminals 78, 73a, 78b, and 7&3 and its other end being connected to a wire 121. Thus the switch blade 79 has four positions numbered 1, 2, 3 and 4; in postion 1 no reslstance is connected between the wires 11a and 12a :and in positions 2, 3, and 4 one of the resistances R31, R32, or R33 is connected between the wires 11a and 12a.

The wires 11a and 12a connect to wires 11 and 12 and as will be presently described one of the resistances of the group of resistances GR1 can be connected into one of the J power control signal circuits, in combinations which will be described.

Adjacent the group of resistances GR1 is a similar group of resistances GR2 including four resistances identitled as R3, R28, R29, and R30 similarly arranged. 3

One end of each of these resistances connects to a wire be'r'noved so that any one of the nect to wires 9 and 10 which as will given predetermined amount or percentage.

Selector Switch will next be groups of resistances GR1 and GR2 may be associated ,of resistances GR2 (that is, one of 9a and the other end of the resistances connects to con- :tact'points or terminals 80, a, 80b and 80c. Cooperable with the terminals 80 to blade'81 which can be moved 80c is a movable switch to contact any one of the contact points 'and'the' other end ofthe blade being connected to the wire 10a. Thus, the switch blade 81 can resistances R3, R28, R29, or R30 isv connected between the wires 9a and 10a. The switch blades 79, and 81 are mounted on the same rotatable shaft which is rotatable by a manually adjustable knob 82 so that the switch as a whole, which may be called the J Suppression Switch, can be set to any one of the positions 1, 2, 3, or 4. The wires 9a and 10a conbe presently described may be connected into any one of the J power control signal circuits, that is, the J power circuit for J 1, J2, J3, or J 4. From the foregoing, it will be observed that when it is desired to reduce the amperage of one or more of the J arcs, one of the resistances of each of the groups of resistance GR1, GR2 is connected into one of the J arc control signal circuits. The size of the resistance inserted is determined by the position of the Suppression Switch so that the arcs which are reduced can be reduced by a It will be noted that in position 1 of the I Suppression Switch, no resistance is connected between the wires 11a and 12a so that the particular I are which is associated with this group of resistances, that is GR1 is not reduced. That is, in position 1 only one J are is reduced, and this are is reduced by 60%, the size of resistance R3 being such as to bring about this reduction. The size of resistances -in two of. the I arcs. The size of theresistances R30 and R33 is suiiicient to bring about a reduction of 40% in two of the I arcs. V

The switching mechanism which will be called the described whereby the two with, that is, whereby one resistance of each of these groups may be associated with given combinations consisting of two Js each. The switching mechanism provides for reducing the amperage of the following combination of J arcs: V

,l. (The firstposition of selector switch) GR2 associated with J 1; GR1 with J 3. r v

2. (Second position of selector switch) GR2 associated with 12; GR1 with J4.

3. (Third position 'of selector switch) GR2 associated with J3; GR1 with J1.

4. (Fourth position of selector switch) GR2 associated with J4; GR1 with J2.

From the foregoing it will be observed that the group the resistances of this group) may be connected into any one of the] circuits, with the other group of resistances GR1 (that is, one of the resistances of the group) being associated with one of the other I circuits. Thus, if it is desired to only reduce the amperage of a single I arc, the I Suppression Switch is placed in position one in which there is no resistance across the wires 11:: and 12a and the amperage of the J are of that particular I. which is associated with the group of resistances GR2 is reduced. The switching mechanism whereby theparticular J or Js are selected to havetheir amperage reduced will next be described, this switching mechanism being identified as J Selector Switch, numeral 85; (it may be well to state at this point that while the manual switches are being described whereby the J are or arcs which it is desired to be reduced are selectively chosen manually, it is to be understood that the actual reduction of the arcs, that is, the amperage of the 'arcs,

prises a shaft 86 which may be rotated by a knob 87 described later.

having a pointer which may be set adjacent any of diiferent positions identified on the drawing by the legend OE and J1, J2, J3, and J4. The characters J1-J4 associated with positions 1, 2, 3, and 4 indicate that that particular J is associated through the Selector Switch with the group of resistances GRZ so that when the J Suppression Switch is in position one, that particular I will have the amperage of its are reduced 60%. The J Selector Switch 85 has associated with the rotatable shaft 86 contact rotors indicated at 88, 89, and 99. The rotatable contactor 88 has rotatable therewith a brushtype contactor consisting of two contact fingers 92 and 93; the contact finger or brush 92 engages a semi-circular contact strip 94 and remains in engagement therewith as the shaft 86 is rotated. The contact finger or brush 93 is operable to engage a number of circularly arranged contact points or terminals identified by the numerals 6a, 8a, 2a, and 4a, these numerals identifying these contact terminals with the particular circuits or circuit portions previously identified by the same numeral. The brushes or fingers 92 and 93 are connected and their effect is to bridge or produce a connection between the contact strip 94 and any one of the terminals 6a, 8a, 2a, or 4a. The contact strip 94 connects to a terminal 11 to which the wire 11 connects as indicated on the drawing, the wire 11 previously having been identified as one of the wires across which the group of resistances included in group GRI may be connected. Diametrically opposed to brushes 92 and 93 are a similar pair of brushes or contact fingers 95 and 96, the brush 96 engaging a semicircular contact strip 97 and the brush 95 being operable to engage, that is contact with, a group of circularly ar ranged contact terminals identified by the numerals 1a, 3a, 5a, and 7a, these numerals identifying these terminals with circuits or circuit portions previously identified by the same numerals. The brushes 95 and 96 are connected and serve to bridge or provide for connecting contact strip 97 with any one of the terminals in, 3a, 5a, and 7a, the contact strip 97 connecting to a terminal to which wire 10 connects, wire 10 having been previously identified as one of the wires across which one of the resistances of group GRZ may be connected.

The Selector Switch 85 is shown in the Off position and in this position the brushes of rotor 88 do not bridge the contact strips 94 and 97 with any of the terminals 1a to Sc; as the shaft 86 is rotated in a counterclockwise direction to positions 1, 2, 3 and 4, it will be observed that brushes 92 and 93 successively bridge contact strip 94 to terminals 6a, 8a, 2a, and 4a; brushes 95 and 96 succesively bridge contact strip 97 to the terminals 1a, 3a, 5a, and 7a.

The rotor 89 of Selector Switch 85 has 10 radial arms or spokes as shown spaced degrees apart with blank spaces identified as B1 and B2 diametrically opposed, the blank spaces having no radial arms or spokes corresponding to the other arms. Each of the radial arms has brushes at its end, or that is, bridging contacts being identified by the numerals 1b to 8b which are arranged as shown, the numerals identifying the contact pairs with circuits or circuit portions previously identified by the same numerals. In addition to the contact pairs numbered 1b to 85, there are a similar pair of contacts, the two contacts being identified by the numerals 13b and 14b which connect to wires similarly numbered 13 and 14. Wire 14 connects to ground and wire 13 will be In the OE position of the Selector Switch as shown all of the contact pairs 1b to 8b are bridged as shown. When the Selector Switch is moved to position 1, contact pairs In and 6b are unbridged, these contact pairs then being opposite the blank spaces B2 and B1. Similarly when the Selector Switch is moved to position 2, contact pairs 31) and 8b are unbridged and similarly opposed contact pairs become unbridged as the Selector Switch is moved to successive positions.

Rotor 90 of Selector Switch 85 has brushes and contactors the same as rotor 88, and they are numbered the same with the identifying number including the letter 0 so that repetition of the description is not necessary. The contact terminals are numbered the same except that the terminals connecting to wires 12 and 9 are numbered 12' and 9, these numerals identifying the terminals with circuits or circuit portions 12 and 9 which is previously described connect to the groups of resistances GRI and GR2.

When the Selector Switch is in the Off position, it will be seen that terminals 13 and 14 of rotor 89 are unbridged so that the wire 13 which connects to the common terminal of the windings or" relays RES and RE9 is disconnected from the grounded connection 14 so that these relays cannot be energized.

The manner in which the groups of resistances GRI and GRZ may be selectively associated with desired individual J power circuits will now be shown.

As previously described, when the Selector Switch is Q in position i, the group of resistances GRZ is to be as sociated with the circuit J1 so that if desired any one of the resistances of this group can be inserted in the control signal circuit for are J1. When the Selector Switch 85; is in position 1, brushes 92 and 93 bridge contact strip 94 to terminal 6a; brushes 9:; and bridge contact strips 9'7 to terminal la; when Selector Switch 85 is in the number 1 position, brushes 92c and 930 of rotor bridge contact strip 940 to terminal 6c; brushes 95c and 96c bridge contact strip 970 to terminal number 10. Circuit 9-itl (and 9aifiu) is now in series with circuit i-2 which is the it power circuit. Tracing this circuit, starting with the control system on Fig. 3 for J power supply, wire number 1 leads to terminal 1c associated with rotor 99, and since contacts lb associated with the rotor 89 are now unbridgcd, the circuit continues through brushes 95c and 96c to contact strip 970 to terminal 9, through wires 9, 9a (one of the resistances of group GRZ), Na, and lid, returning through 10 to terminal 18 and contact strip 97 associated with the rotor 88, thence through brushes as and 95 of the rotor 88, terminal 1a over to terminal 2a of rotor 88 through contact pair number 2b of the rotor 89 which are bridged at this time, to terminal 2c of the rotor 90 and then back through wire 2 to the control circuit for are J1. A similar circuit can be traced out for positions 2, 3, and 4 of the Selector Switch whereby the group of resistances GRZ (that is, one of the resistances of this group) is connected into the controi circuit for arcs J2, J3, and J4 respectively when the Selector-Switch is in these respective positions. Thus, when the Selector Switch is in one of these positions and the J Suppression Switch is in position 1, that particular J are is reduced by 60%, resistance R3 being of a size to produce this reduction and the other J, that is, of the combination of two Js normally reduced, is not reduced at all since as described no resistance is associated with terminal 78 of the J Suppression Switch.

When the Selector Switch 85 is in the Off position,

GRZ. To illustrate the bridging of circuit 1-2 for example, the circuit may be traced starting from the J1 control circuit through wire it to terminal to associated with rotor 98, thence to contact pair 11) associated with rotor 89 (now bridged), thence to contact In associated with rotor 88, to contact 2a, to contact pair 212 of rotor 89 (now bridged) to contact 2c of the rotor 90 and thence through wire 2 back to the negative lead connecting to the cathode of J l. A similar circuit can be traced for each of the circuits 3-4, 5-5 and 7-8 show ing that such circuit is bridged or shunted when the Selector Switch 85 is in the Ofif position.

The foregoing explains how the Selector Switch may be placing one of the resistances of each of groups 6R2 in the control signal circuit of one of the J are come out of the flurry while 11 adjusted to choose a particular combination of two ]s which it is desired tohave the amperage of the are reduced in the event of a flurry associated with one of the ion source units or one of the accelerating electrodes. The above description has also shown how the system may be set up for only reducing the amperage of one of the J arcs if desired. Next will be described how the resistances are automatically connected into the signal circuit of one or two of the Js to produce the desired reduction in amperage for purposes of bringing the system out of the flurry. in the ensuing description the word normal has reference to conditions with power on and the system in steady operation with no abnormalities prevailing.

Referring to circuits 9-10 and ill-12, these circuits are normally bridged or shunted so as to render the groups of resistances GRI and GRZ ineffective, these circuits being controlled by normally closed switches lid and 101 which are actuated by relay RE@ which is normally energized (see Fig. i). it is only when relay R136 is deenergized that switches 1G0 and 101 open thus opening the shunts across circuits and 11-42 and thus GR1 and circuits. The manner in which relay R136 is automatica controlled will be next described.

The control of relay RES is in response to the magnitude of the drain current to the accelerating electrode systein,.by means of a time delay device 102 and a relay R151. The relay REl is controlled by a signal from the accelerating electrode system, the arrangement being such that when the drain current to the electrode system reaches a predetermined relatively high value, relay REl will energize causing relay REo to drop out opening the shunts across circuits 9-10 and 11-12 producing the results already described. The control of relay RE6 is through an electronic time delay device 102 so that after the relay R136 has dropped out it cannot reenergize for an adjustable time delay period which may be six seconds, for example, so that the amperage of one or more of the J arcs is maintained at the reduced value for this given predetermined period to give the system positively time to the J amperage is thus reduced. The electronic time delay device includes a tube 163 having the winding of relay RE6 in the plate circuit thereof. (The winding of relay REG is in series with the winding of a relay R1510 to be referred to later.) The cathode return circuit normally connects to ground through the switch 104 of relay REL this switch normally being closed, relay RE1 normally being deenergized; through contact 105 of relay RE7 which is normally encrgized; through a wire 106; through the switch 107 of relay REZ which is normally energized; and through wire 1 58 to ground indicated by wire 109. Tube 103 has a suppressor grid connected to the cathode as shown and its filament is supplied with power by a circuit X-X (not shown). Tube 103 is a gas filled thyratron tube and its control-grid connects to ground through condenser C3 and connected across this condenser in series are resistance R9 and variable resistance R0. Resistance R10 is connected between the cathode return of tube 103 and ground as shown and resistance R11 is connected between the cathode return and the plate circuit as shown which connects through wire 110 and through fuse 111 and wire to a suitable A. C. power supply V1 as shown.

Tube 1:13 is normally conducting so that there is current in its plate circuit energizing relay R136 so that switches 10d and 101 are closed shunting circuits 9-10 and 11-12 as described above.

Relay REl is controlled by the drain current to the electrode system, the control signal being through a wire 17 which is connected to the ground wire '74 of the accelerating electrode power supply which wire connects to ground as which has a spark shown through a variable resistance R-18 gap H1, connected there-across as CJI to shunt high frequency voltage surges.

through resistance R18.

RBI to energize.

sistance R2 and a resistance I tor ate relay RE1 shown, the spark gap protecting the resistance by serving The signal through wire 17 is therefore a voltage signal which is dependent upon the amount of drain current passing When it reaches a predetermined relatively high magnitude, this signal will cause relay Wire 17 passes through a variable re- RI and then connects to the winding of relay RE1 and thence to ground so that when the signal is of the set predetermined magnitude, relay REE energizes opening switch 104, disconnecting the cathode return of tube 103 from ground. This interrupts the circuit through the tube and relay RE6 deencrgizes, opening switches 100 and 101 which interrupts the shunts across circuits 9-113 and 11-12 and places the groups'of resistances GRZ and GR1 across these circuits. The resuit is that the amperage of one or two of the J arcs is reduced depending upon the position of the 1 Suppression Switch as described above and the one I or the two ls aifected depending upon the position of the Selec- Switch as described above.

Immediately after relay RE1 has been energized as described above, it will be deenergized as will now be described. Relay RE10 has its winding connected in the plate circuit of tube 103 in series with the winding of relay REG so that as soon as REo is deenergized, RE10 will also be deenergized, R1510 normally being energized the same as R136. When relay R1310 deenergizes, it opens contact 115 and closes contact 116. The eflfect of opening contact 115 will be described later. When contact 116 closes, it shunts the winding of relay RBI to ground through a wire 117 which, as shown, connects through contact 116 to the ground wire 10?.

Condenser C1 is'across the winding'of relay RBI and its eilect'is to prevent the actuation of relay RE]. in response to flick sparks at the accelerating electrode. Flick sparks are sudden momentary sparks which do not actubecause of the ground connection through condenser C1, that is the condenser C1, interposesa time delay during which it charges before relay RE1 energrzes.

Condenser C4 is across the windings of relays RE6 and RE10 and its effect is to dampen out the pulsations in the current in the plate circuit of tube 103, this tube being one which conducts current in pulses; thus a fairly steady current is supplied for energizing relays REG and RE10.

As soon as relay REl deenergizes in response to the operation of relay RE10, switch 104 is again closed connecting the cathode return of tube 103 to ground. Tube 103 does not immediately conduct, however, it not conducting until after the exipration of an adjustable time delay period of six seconds which is determined by the adjustment of resistance R8. When switch 104 is opened, the voltage of power supply V1 is across resistances R11 and R10 by way of wire 110 previously described and the ground connection. Due to the voltage drop across R10, a voltage diiierence is now impressed between the cathode of tube 103 and the control grid. in this particular type of tube with a voltage thus impressed, there is rectifying action between the cathode and the grid and a pulsating current flows therebetween which charges the condenser C3, placing a negative bias on the control grid of tube 103; then when switch 104 is closed, tube 103 is prevented from conducting until this bias leaks off, the time required depending on the setting of resistance R8 and R9 connected across C3. Thus, after six seconds tube 103 will conduct and relays R136 and RE10 will reenergize; switches and 101 will reclose shunting circuits 9-10 and 11-12 removing the resistances in circuit with one or two of the I arcs. in other words, after six seconds the J arcs will be restored to normal and at that time the flurry should have been overcome. However,

that is if the accelercurrent is still above the predeterif the flurry has not been overcome, ating electrode drain 13 pressor system will recycle in the manner just described. When tube 1113 is conducting, resistance R19 is shunted and there is no charging of condenser C3.

Our invention additionally provides for automatically taking corrective measures in the system to bring about overcoming a flurry associated with the ion source units, that is, a flurry which is manifested by a relatively high drain current to the ion source unit assembly. This is the current in wire 70 as distinguished from the accelerating electrode drain current in wire 75. The corrective action taken in this instance is to reduce the current in the ion source assembly by emission limiting the control tubes which control the power supplied thereto. The power supply to the filaments of the tubes is regulated by relays RES and R59 in the manner previously described and these relays are controlled in part by a relay RE3 which is responsive to the magnitude of the drain current to the ion source units. Relay R153 has associated therewith a time delay device 120 including a gas filled thyratron tube 121 which operates similarly to tube 193. Relay RE3 and the time delay device 120 control relay RE7 previously referred to, and this relay has contacts which control relay R138 which as described above exerts control over the current to the ion source units. The signal for controlling the relay RES is through wire 19 which connects to the ground wire 67 of the power supply 41) which supplies power for the ion source units. Ground wire 67 connects to ground through a variable resistance R19 which has a spark gap H2 connected thereacross, the spark gap protecting the resistance by serving to shunt high frequency voltage surges. Depending upon the magnitude of the drain current to the ion source units, there will be a voltage developed across the resistance R19 and the signal through wire 19 will depend upon the magnitude of this voltage. The signal through wire 1? is through a variable resistance R4 and the resistance R5 and through the winding of relay RES and back to ground. Condenser C2 is connected across the winding of relay RES, and it provides for a time delay of approximately one second to prevent actuation of relay RE3 in response to flick sparks at the ion source units. Relay RE3 will thus energize in response to a predetermined value or drain current to the ion source units, and when it energizes it opens switch 125 which is normally closed, thus opening the ground connection of the cathode return of tube 121, this ground connection being through wire 126, switch 128 of relay RE2, this switch being normally closed, and through wire 1118 and to the ground wire 169. Opening of switch 125 interrupts the circuit through tube 121, and this deenergizes relay RE7, the winding of which is in the plate circuit of tube 121. When relay RE7 deenergizes, it closes switch 127 which is normally held open. Closing of switch 127 completes a circuit energizing relay RES, this circuit being from the wire 21) through wire 110, wire 129, switch 127, wire 130, and wire 22 through the winding of relay RES, wire 13, through Selector Switch 85 and through the wire 14 to ground. When relay RES is energized, it opens switches as, 57, and 53 which opens shunts around the resistances R21, R22, and R23, thus placing additional resistance in each of the leads from the three phase power supply 15 to the transformers supplying power for the filaments of tubes 68 and 69. When, thus emission limited, the amount of current which the tubes will pass is limited and accordingly the current through the ion source units is reduced.

Immediately after the energization of R153 it is again deenergized by the closing of contact 131 which closes when relay RE7 is deenergized. Contact 131 completes a shunt across the winding of relay RES through wire 132 connecting from wire 19 through resistances R4 and R5 through contact 131, wire 106, switch 107 and wire 1% back to the ground wire 109. The winding of relay RE3 being shunted it immediately deenergizes closing switch 1 1 125 and thus again completing the ground connection of the cathode return of tube 121.

During the time that switch 125 is opened, a voltage from the source V1 is on both the cathode and the grid of tube 121. It will be observed that the grid of tube 121 connects to ground through condenser C5, this condenser having resistance R4 and variable resistance R13 connected in series thereacross and resistance R15 being connected between ground and the cathode return of tube 121. Resistance R16 is connected between the cathode return of tube 121 and the plate circuit. When switch 125 is open, voltage due to the drop across resistance R15 is impressed between the cathode and the grid of tube 121 which is connected to ground; due to the rectifier action of this tube similarly to that of tube 102, there will be a pulsating current flow between cathode and grid which will charge condenser C5, placing a negative bias on the control grid of tube 121; then when switch 125 is closed, tube 121 is prevented from conducting until this bias leaks off, the time required depending on the setting of resistance R13 and R4 and this may be five seconds. When tube 121 is conducting, resistance R15 is shunted and there is no charging of condenser C5. Thus, after the current in the ion source units has been reduced in response to a flurry, it remains reduced for a period of five seconds at which time tube 121 will again be conducting and the current limitation will be removed. If the flurry has not been overcome, the system will recycle, again reducing the current in the ion source units, that is, the source assembly.

The automatic system for limiting the current in the ion source assembly is interlocked with the automatic system for reducing the amperage of one or more I arcs So that whenever the current in the ion source assembly is automatically limited, the automatic system for reducing the amperage of one or more I arcs will automatically and simultaneously function. The interlock is provided by contact 1115 of relay RE7, relay RE7 deenergizing and opening contact as described whenever the automatic system for reducing the ion source assembly current operates. Opening contact 105 disconnects the cathode return of tube 103 from ground the same as switch 1114- docs and thus the system for reducing the arc amperage functions the same as described above.

When the ion source assembly current has been reduced in response to operation of relay RE3, the relay RE7 will be reenergized after the five second time delay period as described above. Relay RE7 does not reenergize until after the expiration of this time period so that the six second time delay period of tube 103 cannot begin until the live second time delay of tube 121 has expired, that is, until contact 105 has reclosed. Thus, when the limitation on the ion source assembly current is removed, the amperage of one or more arcs is still at the reduced value which is not restored until the six second time delay period provided by tube 103.

The ion source assembly or a unit thereof may be in a flurry which is not overcome by one cycle of operation of the current reducing system, and the system may recycle several times attempting to overcome the flurry. Our invention provides an automatic arrangement whereby after a predetermined number of recycles which do not overcome the fiurry, the current in the ion source assembly will be reduced by a second increment to insure that the flurry will be overcome. The automatic arrangement for providing this function will next be described. Relay RE10 as described above is normally energized and drops out whenever device 102 functions and whenever device 12% functions since as described device 192 functions whenever device 1211 does. Contact of relay RE10 controls a circuit including wire 1411 which shunts the electric heater 142 of a thermostatic time relay RE4 so that this heater is rendered effective to heat when contact 115 opens. The relay RE4 includes a temperature responsive element operable to bridge a pair of conabove. The arc amperage of one or tacts 143 and 144 when sufficiently heated by heater 142. Contacts 143 and 144 control a shunt circuit through resistance R27 around the winding of a relay RES which is normally supplied with power through resistance R34 from a secondary 139 of the transformer T15 and the wire 141. Transformer T15 has a primary 155 connected to a power source V2. Relay RES is normally energized through the circuit just described and it controls a contact 146 which is normally closed, a contact 148 which is'normally open and a contact 147 which is normally open. Whenever switch 127 of relay RE7 closes in response to deenergization of this relay, a circuit is completed through switch 12-7 and wire 13%, wire 145, contact 146, variable resistance R20, heater 142 and wire 141 to the ground wire 199. Thus, during the time that switch 127 is closed, current is supplied to the heater 142 and it heats the element which may bridge contacts 143 and 14-4. Resistance R is so adjusted that if device 12-1 recycles three times, contacts 143 and 144 will be bridged shunting relay RES which will deenergize opening contact 146 and closing contacts 143 and 147. Closure of contact 147 completes a circuit therethrough and through wire 149 and Wire 23 to the winding of relay RE9 and thence through wire 13 and through the selector switch and wire 14 to ground. switches 6t), 61 and 62 which opens the shunts around the variable resistances R24, R25, and R26 which adds an additional increment of resistance in each of the power leads supplying power to the filaments of tubes 68 and 69; thus the current in the ion source assembly is'reduced by an amount positively insuring that the unit or units affected be brought out of the flurry. Closure of contact 147 completes another circuit therethrough and through wire 149 and wire 15c and contact 148 through the heater 142 so that contacts 1d?) and 144 remain bridged thus keeping relay RES deenergized and as a result keeping RE9 energized until contact closes shunting heater 142. This will'not happen until six seconds after the device 129 stops recycling finally. At this time the time delay period of device 192 will be begun and since device 123 has stopped recycling, the flurry having been overcome, the time delay period of device 102 will be allowed to continue and after the six second period relay REltl will energize and contact 115 will close completing the shunt across heater 142 so tinue and contacts 143 and 14 will be unbridged after cooling, allowing'relay RES to reenergize, opening contact 14S and opening the heater circuit, closing contact 146 and opening contact 1M, deenergizing relay RE9 and allowing switches 6%, 61, and 62 to reclose. Switch 1 127 of relay RE7, of course, opened when relay RE7 was energized after the live second time delay period of device 12%) and relay RE3 was deenergized at this time to reclose switches 56, 57 and 58. I The overload responsive device 38 previously referred t to is conventional in itself and in the event of overloads may cut off power to the entire system. The conditions which bring about operation of devices 1(l2 and 12% may not necessarily, however, be such as to cause the overload device 33 to function. Or devices W2 and may function, with device 33 then proceeding to function. Our arrangement provides, however, for causing the controls 192 and 128 to function whenever the overload responsive device 38 functions. This control is through switch 35 which opens when circuits. Opening of switch 35 deenergizes relay RE2, opening switches lit! and 128. Relay RE). is normally energized through a circuit from wire 2b to wire 156, switch 35, wire 157, relay REZ and wire 158 back to ground. When switches 1%7 and 128 open, the cathode return of both tube 103 and tube 121 is disconnected from ground thereby interrupting the circuit through these tubes bringing about the functions described more arcs is reduced as described and the ion source assembly current is limited.

This energizes relay RE? opening .11.

that heating will discondevice 38 opens the power After reenergization of relay REZ in response to restoration of power by device 33 the time delay period of device 120 comm nces. After relay RE7 is reenergized closing contact the time delay period of device 162 begins, at the expiration of which the amperage of the are or arcs is restored as before. The time delay periods are successive. Thus any time device 38 cuts off the power, when it returns the ion source assembly current will be limited and the amperage of one or more arcs will be reduced to thus overcome the disturbance which caused the power to cut oil.

Briefly summarizing the entire system, the 'Selector Switch 85 selects the one or two Js which are to have their are amperage reduced in the event of a flurry at the accelerating electrode. The I Suppression Switch is used for the uully adjusting the amount or percentage by which the arc amperage of the two Is selected is reduc d or one i if it is desired to reduce just one I. The device M32 embodying a time delay of six seconds responds automatically to reduce the arc amperage of one or two ]s, as selected, in response to a relatively high current drain to the accelerating electrode system. The device 162 through relay REitl renders the thermostatic relay R154 operative. The device 12b embodying the five second time delay feature responds to the magnitude of the current drain to the ion source assembly and is operable to reduce the current in the ion source assembly by a given increment and to restore normal conditions after a time delay period of five seconds. The device 120 whenever it functions causes the device lilZ to function simultaneously in its regular manner, but the device 120 being so interlocked with the device 1&2 that the time delay period of device 1&2 begins after the expiration of the time delay period of device 124 so that the arc amperage is restored to normal only after the limitation on ion source assembly current has been removed (i. e.) the ion current is restored to normal at a time when the arc amperage is at the temporary reduced value. Device 12 may recycle three times in attempting to overcome the flurry, and if the flurry is not overcome after three cycles, the thermostaticrelay R134 will function to cause the ion source assembly current to be reduced by a second increment so that the'total reduction is sufficient to positively insure overcoming the flurry. After thus overcoming the flurry, the ion source assembly current and the arc amperage will be restored to normal as before. In the event of power being cut off by the overload responsive device 3%,both device 1tl2 and device 123 will function in the manner described, the time delay periods being successive after power is restored.

The embodiment of our invention disclosed herein is representative of its preferred form. The disclosure is to be interpreted in an illustrative rather than a limiting sense, the scope of the invention being determined in accordance with the claims appended hereto.

We claim:

1. ln apparatus of the'character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, and means for controlling the arc in response to current in the accelerating electrode.

2. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, and means for reducing the amperage of the arc in response to a predetermined accelerating electrode current.

3. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith and means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period.

4. In apparatus of the character described, in com- 17 bination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for reducing the amperage or the arc in response to a predetermined accelerating electrode current, and means for preselecting the amount which the arc amperage is reduced.

5. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, and means for temporarily reducing the amperage of the arc in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, said amperage reducing means also including recycling means for again temporarily reducing the amperage of the are immediately after the time delay period it the accelerating electrode current has not reduced.

6. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, power supply means for said ion source, an overload responsive device associated with said power supply means for reducing the power supplied thereby, and means for actuating said are amperage reducing means in response to operation of said overload responsive device.

7. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for controlling the arc in response to current in the accelerating electrode, means for maintaining said ion source at a relatively high potential and means whereby the arc is also controlled in response to current through said ion source.

8. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for reducing the amperage of the arc in response to a predetermined accelerating electrode current, means for maintaining said ion source at a relatively high potential and means whereby said are reducing means are also responsive to current flow through said ion source.

9. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, means for maintaining said ion source at a relatively high potential and means whereby said are reducing means are also responsive to current flow through said ion source.

10. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for temporarily reducing the amperage of the arc in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, said amperage reducing means also including recycling means for again temporarily reducing the amperage of the are immediately after the time delay period if the accelerating electrode current has not reduced, means for maintaining said ion source at a relatively high potential and means whereby said are reducing means are also responsive to current flow through said ion source.

11. In apparatus of the character described, in combination, means forming an ion source of the arc type,

an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential and means responsive to current flow in the ion source for controlling the arc.

12. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, and means responsive to a relatively high current fiow through the ion source for reducing the arc current.

13. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the are current in response to a predetermined value of current in the ion source, and time delay apparatus for rendering said are reducing means inactive after a. predetermined time delay period.

14. In apparatus of the character described, in combination, means forming an ion source or" the arc type, an accelerating electrode associated therewith, means for main taining said ion source at a relatively high potential, means for temporarily reducing the arc current in response to a predetermined value of current in the ion source, time derendering said are reducing means inactwo after a predetermined time delay period, overload responsive means for reducing the power supplied to the ion source and means controlled thereby for actuating the are reducing means. i

15. In apparatus of the character described, in combination, means forming an ionsource of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential and means responsive to a relatively high current flow through the ion source for substantially reducing the current fiow.

. 16. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for at a relatively high potential,

17. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for source at a relatively high potential,

18. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source and means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current.

19. In apparatus of the character describe-d, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for 20. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, and means for controlling the arc in response to current in the accelerating electrode.

21. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period and means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current.

22. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, and means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period.

23. In apparatus of the character described, in combination, means-forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, means for temporarily reducing the arc amperage in'response'to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period and means whereby the time delay period of the arc reducing means begins at the expiration of the time delay period of the ion source current reducing means.

24. In apparatus of the character described, in combination, means forming an ion source of the arc type, an

accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential.

means for temporarily reducingthe ion source current in response to a predetermined value of current in the ion source, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, and means whereby the are reducing means is also actuated in response to 'ion source current reducing means.

25. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relativelyhigh potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, timedelay apparatus for rendering said current reducing means inactive after a'predetermined'time delay period, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, and means whereby the arc reducingmeans is also actuated in response to ion source current reducing means.

means including time t in the ion source, time delay apparatus 26. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, and means whereby the arc reducing means is also actuated in response to ion source current reducing means.

27. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, means whereby the are reducing means is also actuated in response to ion source current reducing means, and means whereby the time delay before the arc is restored to normal begins at the expiration of the time delay period at the end of which the ion source current reducing means is rendered inactive.

28. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for reducing the amperage of the arc in response to a predetermined accelerating electrode current, means for maintaining said ion source at a relatively high potential,

means whereby said arc reducing means are also responsive to current flow through said ion source, automatic recycling overload responsive means associated with the ion source and accelerating electrode and means whereby said overload responsive means is operable to actuate said arc reducing means.

29. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last delay apparatus for restoring .the arc amperage to normal after a predetermined time delay period, means for maintaining said ion source at a =relatively high potential, means whereby said are reducing means are also responsive to current flow through said ion source, recycling overload responsive means associated with the ion source and accelerating electrode and means-whereby said overload responsive means is operable to actuate said are reducing means.

30. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predeterminedvalue of current for rendering said current reducing means inactive after a predetermined time delay period, recycling overload responsive means associated with the ion source and accelerating electrode and means whereby said overload responsive -means-is operable to actuate said current reducing means.

31. In apparatus of the character described, in combination, means forming an ion sourceof thearc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the Ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, recycling overload responsive means associated with the ion source and accelerating electrode, and means whereby said overload responsive means is operable to actuate said arc reducing means and ion source current reducing means.

32. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a pedetermined time delay period, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, means Whereby the are reducing means is also actuated in response to the ion source current reducing means, means whereby the time delay before the arc is restored to normal begins at the expiration of the time delay period at the end of which the ion source current reducing means is rendered inactive, automatic recycling overload responsive means associated with the ion source and accelerating electrode and means whereby said overload responsive means is operable to actuate said are reducing means and ion source current reducing means.

33. In a calutron, in combination, ion source means employing a plurality of arcs, automatic means for temporarily reducing the amperage of at least one are during operation, and manual switching means for prc-selecting the arc to be reduced.

34. In a calutron, in combination, ion source means employing a plurality of arcs, automatic means for temporarily reducing the amperage of a group of arcs during operation and manual switching means for pre-selecting the arcs to be included in said group.

35. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, said ion source current reducing means being operable to recycle after said period and means responsive to a predetermined number of recycles thereof to reduce said ion source current by a second increment.

36. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said ion source current reducing means being operable to recycle after said period and means responsive to a predetermined number of recycles thereof to reduce said ion source current by a second increment.

37. In apparatus of the character described, in com- 22 bination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, means whereby the time delay period of the are reducing means begins at the expiration of the time delay period of the ion source current reducing means, said ion source current reducing means being operable to recycle after its time delay period and means responsive to a predetermined number of recycles thereof to reduce said ion source current by a second increment.

38. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion source at a relatively high potential, means for temporarily reducing the ion source current in response to a predetermined value of current in the ion source, time delay apparatus for rendering said current reducing means inactive after a predetermined time delay period, means for temporarily reducing the arc amperage in response to a predetermined accelerating electrode current, said last means including time delay apparatus for restoring the arc amperage to normal after a predetermined time delay period, means whereby the arc reducing means is also actuated in response to the ion source current reducing means, means whereby the time delay before the arc is restored to normal begins at the expiration of the time delay period at the end of which the ion source current reducing means is rendered inactive, said ion source current reducing means being operable to recycle after its time delay period and means responsive to a predetermined number of recycles thereof to reduce said ion source current by a second increment.

39. in a calutron, in combination, an ion. source, means for maintaining said source at a relatively high potential with respect to ground, control means for reducing the current in the ion source in response to a condition indicative of sparking at said source.

40. In a calutron, in combination, an ion source, means for maintaining said source at a relatively high potential with respect to ground, control means for reducing the current in the ion source in response to a condition indicative of sparking at said source, said control means including a vacuum tube for controlling the current flow and means for emission limiting said tube.

41. In a calutron, in combination, an ion source, means for maintaining said source at a relatively high potential with respect to ground, control means for reducing the current in the ion source, said control means including a vacuum tube and means responsive to current flow in the ion source for emission limiting said tube to control the current flow.

42. In a calutron, in combination, an ion source, means for maintaining said source at a relatively high potential with respect to ground, control means for reducing the current in the ion source, said control means including a vacuum tube and means responsive to current flow in the ion source for emission limiting said tube to control the current flow, and time delay means for causing said tube to be emission limited for a predetermined time delay period.

43. In a calutron, in combinaation, an ion source, means for maintaining said source at a relatively high potential with respect to ground, control means for reducing the current in the ion source, said control means including a vacuum tube and means responsive to current flow in the ion source for emission limiting: said tube to control the current flow, time delay means for causing 23 said tube to be emission limited for a predetermined time delay period, said emission limiting and time delay means being operable to automatically recycle and means whereby after a predetermined number of recycles said tube is emission limited by a second increment.

.44. In apparatus of the character described, in combination, means forming an ion source of the arc type, an accelerating. electrode associated therewith, means for maintaining said ion source at a relatively high potential, and means for reducing the ion source current and the are amperage in response to a predetermined relatively high ion source current.

45. In apparatus of the character described, in combination, .means forming an ion source of the arc type,

an accelerating electrode associated therewith, means for maintainingsaid ion source at a relatively high potential, means for reducing the ion source current and the are amperage in response to a predetermined relatively high ion source current and time delay means for rendering the ion source current reducing means inactive after a time delay periodand for restoring the. arc to' normal 0 after a further period.

46. in apparatus of the character described, in combination', means forming an ion source of the arc type, an accelerating electrode associated therewith, means for maintaining said ion' source at a relatively high potential, means for reducing the ion source current and the arc amperage in response to apre'determined relatively high ion source current and overload responsive means operable to actuate both the ion source current reducing means and are reducing means.

No references cited. 

9. IN APPARATUS OF THE CHARACTER DESCRIBED, IN COMBINATION, MEANS FORMING AN ION SOURCE OF THE ARC TYPE, AN ACCELERATING ELECTRODE ASSOCIATED THEREWITH, MEANS FOR TEMPORARILY REDUCING THE ARC AMPERAGE IN RESPONSE TO A PREDETERMINED ACCELERATING ELECTRODE CURRENT, SAID LAST MEANS INCLUDING TIME DELAY APPARATUS FOR RESTORING THE ARC AMPERAGE TO NORAMAL AFTER A PREDETERMINED TIME DELAY PERIOD, MEANS FOR MAINTAINING SAID ION SOURCE AT A RELATIVELY HIGH POTENTIAL AND MEANS WHEREBY SAID ARC REDUCING MEANS ARE ALSO RESPONSIVE TO CURRENT FLOW THROUGH SAID ION SOURCE. 